Brake control for preventing locking during the braking of a rotating wheel

ABSTRACT

The combination, with a rotatable wheel and fluid-pressureactuated brake for braking rotation of the wheel, of a mechanical control for preventing the wheel from locking during braking in which a frequency sensitive driven vibrating system having a predetermined resonant frequency is forced to vibrate at frequencies proportional to the rotational speed of the wheel and wherein displacement of one component of the vibrating system through a predetermined amplitude during forced vibration thereof at the predetermined resonant frequency actuates a fluid flow control for precluding increase in braking effect exerted on the wheel.

United States Patent [1 1 Holst et al.

[ E Re. 28,562

[ Reissued Sept. 30, 1975 BRAKE CONTROL FOR PREVENTING LOCKING DURINGTHE BRAKING OF A ROTATING WHEEL [76] Inventors: Jan-Olov M. Holst,Laduvagen 12,

75247 Uppsala; Rolf E. Nordstrom, Johan Enbergsvag 48A, 17161 Solna;Christer U. Ekenberg, Apoteksvagen 6, 74100 Knivsta, all of Sweden [22]Filed: Oct. 18, 1973 21 Appl. No.: 407,501

Related US. Patent Documents Reissue of:

[64] Patent No.: 3,614,176

Issued: Oct. 19, 1971 Appl. No.: 826,180

Filed: May 20, 1969 {52] US. Cl 303/61; 303/21 R [51] Int. Cl. 360T 8/06[58] Field of Search 303/21, 24, 6, 61-63,

[56] References Cited UNITED STATES PATENTS 3,032,995 5/1962 Knowles .1303/21 FP UX 3,124,220 3/1964 Kell 303/21 FP X 3,231,315 1/1966 Turnbull303/61 3,276,822 10/1966 Lister et all 303/21 FP X 3,361,487 1/1968Vriend 1 1 .1 303/61 3,495,879 2/1970 Sharp 188/181 A X 3,514,162 5/1970Erlebach et a1, 303/21 FP Primary E.taminer-Duane A. Reger Attorney,Agent, or FirmParrott, Bell, Seltzer, Park & Gibson [57] ABSTRACT Thecombination, with a rotatable wheel and fluidpressure-actuated brake forbraking rotation of the wheel, of a mechanical control for preventingthe wheel from locking during braking in which a fre quency sensitivedriven vibrating system having a predetermined resonant frequency isforced to vibrate at frequencies proportional to the rotational speed ofthe wheel and wherein displacement of one component of the vibratingsystem through a predetermined amplitude during forced vibration thereofat the predetermined resonant frequency actuates a fluid flow controlfor precluding increase in braking effect exerted on the wheel.

30 Claims, 18 Drawing Figures Reissued Sept. 30,1975 Sheet 1 of 11 Re.28,562

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BRAKE CONTROL FOR PREVENTING LOCKING DURING THE BRAKING OF A ROTATINGWHEEL Matter enclosed in heavy brackets I: appears in the originalpatent but forms no part of this reissue specification; matter printedin italics indicates the "additions made by reissue.

The invention refers to a brake control adapted to prevent locking whena rotating wheel is braked. The invention is particularly adapted toprevent locking during the braking of a vehicle wheel and the inventionwill hereafter be described in connection with the braking system of avehicle. Yet, the invention is not re stricted to this field of use andmay alsobe applied in connection with many other fields of use in whicha rotating wheel is braked with the aid of a brake circuit and wherelocking must not occur during [bracking I braking.

Brake systems as used at[ prewent 1 present in vehicles exhibit theserious drawback that when the friction between the wheels of thevehicle and the rod surface is exceeded during braking locking willoccur involving rapid braking of the vehicle wheel to standstill. Due tosuch locking the vehicle will start skidding and will get out ofsteering control. The most severe risk is caused by a locking of boththe rear wheels of the I: vehcle 1 vehicle whereas during locking of thefront wheels of the vehicle the directional stability is maintained andskidding will not occur. When both of the rear [wheels] wheels of thevehicle are locked skidding phenomena will immediately appear and thedriver will experience great difficulties when trying to hold a steadycourse. Thus. there is an urgent needof simple devices preventingvehicle [whkels 1 wheels from locking and thereby eliminating thepreviously mentioned skidding gtendencies I tendencies.

Various systems have previously been proposed for the purpose ofavoiding locking during braking of vehicle wheels. One such system isbased on the use of an additional measuring wheel adapted to sense theactual speed of the vehicle in relation to the ground, the value foundduring such measurement being compared in a comparison device with thespeed measured for the various vehicle Wheels. When a certain'differenceis detectcd between these two speed values a system will be brought intoaction to release the brake effect applied. This system is complicatedand expensive in manufacture and, due to the delicacy of the electriccomponcnts, it is unsuitable for use under the heavy stresses producedby the shocks and the like experienced dur ing operation of the vehicle.

Also in brake systems of the pneumatic-type regulators have beenpreviously known. One such system makes use of a rotating mass havingthe same speed as the weheel 1 wheel to be braked. During a heavybraking of the wheel this rotating mass due to its I: intertia] inertiawill not be braked at once,. a relative movement taking place betweenthis mass and a sensing device connected to the drive shaft of the massand acting against a cam device on the heavy mass. This relativemovement will laterally shift the sensing device to actuate a valvemember such as to vent the pneumatic brake circuit and to release thewheel from brake actin] action. This arrangement is only adaptable topneumatic systems because in a hydraulic system hydraulic oil wouldescape whenever the control is actuated. Morem er the arrangement isexpensive to manufacture and is not either fully reliable and for thesereasons the system has not been widely accepted.

According to the present invention there is provided a brake controleliminating the problems which, as mentioned above, have beenencountered in previously known brake controls. Theinvention provides abrake control having few movable parts, small dimensions and ahighdegree of reliability. The device is easily manufactured and may beproduced at low cost.

The main object of the invention is a brake control preventing a'wheelfrom looking during braking, provided with a member connected to thebrake system of the wheel and adapted to be controlled by a sensingdevice for temporary removal of the applied brake action. The inventionis particularly characterized in that the I: we nsing] sensing device isadapted to be, preferably mechanically, actuated for reciprocatingmovement by driving pulses proportional to the rotary speed of thewheel, the sensing device being connected to a resilient element havinga heavy mass to form a swinging system which at its natural resonantswinging frequency will react to said driving pulses by performing anincreased swinging amplitude at i which the system actuatcs a valvemember to release the brake effect applied.

The device according to the present invention comprises a unit which maybe incorporated into existing vehicles as well as vehicles underconstruction. In the normal brake circuit of the vehicle a valve unit isincorporated which, on the one hand, is able to close he] the conduitthrough which brake fluid is supplied to the wheel brake cylinder and,on the other hand, may act as a pumping unit to release the brakingpressure previously applied to the wheel brake cylinder. As a means forcontrolling the valve and pump unit there is provided a sensing meansadapted to receive reciprocating motion impulses from the rotatingwheel. Such impulses received by the sensing device are applied to aswinging mass which under the action of impulses I correwpondingcorresponding to the natural reso nant swinging frequency of the systemI: wil wiIl exhibit an increase in amplitude, this increase being usedto control the valve and pump unit such as to interrupt the supply ofpressure fluid and to release previously applied braking pressure fromthe wheel brake I: cyinder] cylinder by a pumping action of the valve I:andpump] and pump unit.l-lereby the braking action is temporarilyreleased from the wheel and as the locking is thus counteracted and thewheel will not assume a zero velocity the ability of the wbeel wheel toabsorb side forces will remain substantially unimpaired and the skiddingrisk is [subwtantially substantially reduced.

la the continuing development it has been discovered to be an importantfactor to increase the frequency of the device controlling the operationof the valve and in accordance therewith it is an object of the presentI: tinvention] invention to provide an arrangement adapted to increasethe frequency of the cycle ofoperation of the valve in relation to thefrequency received from the I impuls] impulse generator.

Further objects and features of the present invention will appear fromthe enclosed claims.

The invention will be described in greater detail by reference to thedrawing and in respect to embodiments adapted to be connected to thebrake circuit system of a motor vehicle. In the drawing,

FIG. I is a schematic representation of the device according to thepresent invention,

FIG. 2 is a graphic representation showing the swigning] swingingamplitude of the system during braking of a wheel,

FIG. 3 is a sectional elevation of an embodiment of the brake controlaccording to the invention,

FIG. 4 is a sectional elevation of another embodiment of the brakecontrol,

FIG. 5 is a schematic view, partly in section, of the brake controlaccording to the present invention,

FIG. 6 is a schematic representation, partly in section, of the brakecontrol provided with a modified swinging mass and a transfer deviceacting between the swinging mass and the valve unit, also the valve unitbeing modified in relation to that shown in FIG. 5,

FIG. 7 is a schematic view, partly in section, similar to FIG. 6 butshowing a modified transfer device,

FIG. 8A is a plan view and FIG. 8B is an elevation, partly in section,in a plan turned 90 in relation to FIG. 8A of an embodiment which on theone hand comprises positive guiding means acting between the swingingmass and the transfer member controlling the valve unit and on the otherhand, a torsion spring replacing the coil spring shown in the previousFigures,

FIG. 9 is a sectional view of another modified embodiment of thetransfer device acting between the swinging mass and the transfer membercontrolling the valve,

FIG. 10A is a plan view, in part in section, of an embodiment, in whichthe valve unit is disposed at right angles to the plane in which theswinging mass is oscil lating,

FIG. 10B is an elevation of the same embodiment seen along line VlB-VIBfrom the right in FIG. "IA,

FIG. 10C is an elevation of the same embodiment as shown in FIGS. "IAand NB, viewed along line VICVIC downwardly in FIG. [0A,

FIG. 11 is a schematic elevation, partly in section, of an embodiment ofthe invention in which the transfer member is a stiff resilient stripelement and in which the valve unit is controlled from the opposite sidein relation to the swinging mass as compared with the preceding Figures.

FIG. 12A is a sectional view of a device adapted to be inserted betweenthe incoming rotatable shaft and the impulse I: gnerator] generator forthe purpose of reducing the generating I freqeuency] frequency to enablethe system more quickly to go down to the cricital 1 critical naturalresonant swinging frequency,

FIG. 12B is a section along line Il in FIG. 12A,

FIG. 13 is a graphic representation illustrating the number ofrevolutions obtained by the use of the device according to FIG. 12 inrelation to the time and FIG. I4 is a sectional view ofa practicalembodiment of a particularly compact construction enabling the unit tobe attached adjacent the rear wheels of a vehicle.

The device which may be incorporated into the brake system of both newand old motor cars comprises a sensing device I contacting a member suchas a cam for receiving driving pulses corresponding to the angularvelocity of the wheel, said sensing device at its rear end beingconnected with a resileint] resilient element 2, such as a helicalspring, said element being made of material having low intrinsicattenuation. Spring 2 is connected to or integral with a heavy mass 3which at its end opposite to the sensing device merges into a reducedelongate part 4. Through a sealing gasket 6 part 4 extends into ahousing 11, hereinafter designated as valve housing. Against the outerend S of part 4 abuts a ball 8 which by means of a spring 12 is pressedagainst a valve seat 7 provided around an aperture 7a in a wall I7. Ball8 and spring 12 are disposed within a chamber I0 of valve housing 11which chamber 10 by means of wall 17 is separated from another chamber 9of the valve housing 11. Normally ball 8 will not be fully seated onseat 7 because part 4 extending from the heavy mass 3 with its end 5slightly forces back ball 8. During braking, brake fluid will enterthrough an inlet 13 into chamber 10 and will pass through aperture 7ainto chamber 9 and further to the brake I: cyinder] cylinder thrugh]through an outlet 14. During normal braking from high velocities thebrake control according to the present invention will not inerfereinterfere with the action of the normal brake system of the vehicle.However, the brake control will come into action at a speedcorresponding to a I: cricitcal I critical frequency of the swingingsystem comprising the sensing device 1, spring 2 and mass 3.

The operation of the device is as follows. Brake fluid under pressure issupplied from the main brake cylinder through the inlet 13 into chamber10 and further [thorugh through aperture 7a into chamber 9 to betransferred through outlet 14 to the wheel brake cylinder of thevehicle. In this initial phase of operation ball 8 with the aid of theforcibly introduced brake fluid will urge rod 4 and the heavy mass 3 tothe left in FIG. 1, this movement being transferred by the spring to thesensing device 1 which is urged into abutment against said cam member orthe like. This cam member will impart to the sensing device 1 alongitudinally reciprocating movement as indicated by the arrow to theleft in FIG. I, said movement being transferred to the swinging systemI, 2, 3, 4 with a slight attenuation due to spring 2. During continuedbraking the frequency of this movement will diminish and at apredetermined frequency which suitable corresponds to a peripheralvelocity within the range of 10 to 20 kilometer/hour of the wheel thisfrequency will be within the I cricital 1 critical resonant swingingrange of the swinging system causing the swinging amplitude to growsubstantially as shown in the diagram of FIG. 2. Hereby the movementimparted to the sensing device 1 is increased and part 4 extending fromthe mass is moved sufficiently far to the left in FIG. 1 tot enabe Ienable valve ball 8 to become seated on seat 7. Portion 5 of elongatepart 4 will then get out of contact with ball 8 which thus will be urgedinto contact with seat 7 by fluid pressure action from the inlet 13 andby spring 12. Thus, no further increase of the brake force will comeinto action in chamber 9 of valve housing 11 where outlet 14 isprovided. During continued movement to the left of spring 2 with itsheavy mass 3 and its elongate extension 4 a pumping effect will beexerted because the volume of chamber 9 will be increased by part 4moving to the left while ball 8 completely closes chamber 9. Herebybraking fluid will be pumped back from the outlet 14 whereby the brakeeffect is released from the wheel. Due to release of the brake effectthe wheel will again pick up speed and the cam member transferring themovement to the sensing device 1 will operate at increased speedincreasing the oscillating frequency to a value above the resonantswinging frequency of the swinging system, the increase in amplitudethereby being removed and the swinging movement being so reduced thatend portion 5 of part 4 will urge ball 8 away from its contact with seat7. Hereby braking pressure may again be transferred from the inlet 13 tochamber 9 and further to outlet 14 whereby the wheel is again exposedfor braking action. By this action which is repeated several times everysecond lockihg of the braked wheel will be prevented because the brakeaction will be released at a rotational speed of the wheel correspondingto the resonant oscillating frequency of the swinging system 1, 2, 3, 4,5.

In FIG. 2 there is schematically shown the oscillating amplitude atvarying speeds. The values at which the increase in amplitude will takeplace may be chosen arbitrarily. the spring and heavy mass being chosenon the basis of the formula m V k/m where w= the angular velocity of thewheel, k the spring constant and m the mass. In FIG. 2 the criticalresonant oscillating frequency has been chosen at a value correspondingto a peripheral velocity of the Wheel of 17 kilometer/hour.

FIG. 3 shows a typical construction ofa practical embodiment of theinvention. This construction is particularly compact to enable thedevice to be used whenever small dimensions are important requirement,eg at the rear I: wbeels wheels of a motor vehicle. The sensing device 1is caused to perform a I: reciporacting reciprocating movement in thedirection of the arrow at the left end of FIG. 3, this recriprocatingmovement being transferred to spring 2 with the heavy mass 3, theelongate part 4 with its end portion 5 contacting ball 8. While theoutlet opening 14 from chamber 9 is shown provided with a restriction,any suitable construction may be used for obtaining correct flowconditions.

FIG. 4 shows a modified embodiment of the invention. The left portion ofthe device comprising the sensing device 1, spring 2, the heavy mass 3and the elongate part 4 has the construction dewcribed describedpreviously whereas the right-hand part compriwing comprising the valveelement proper is moditied in comparison with FIG. I. For ball 8 anelongate sliding valve body 5 such as a spool integral with part 4 hasbeen substituted, said valve spool body having an axial bore 18. Thevalve body is longitudinally movable within housing 1 l which issubdivided into three chambers l0, l5, 9 by partition gaskets 7, 16. Thevalve spool body extends into chamber 9 through a gasket 6. Bore 18 isin communication with chamber 15 via a port 18a. Fluid pressure isintroduced through inlet 13 and is passed via chamber 15 and port 18ainto and through bore 18 to chamber to be discharged through outlet 14to the brake cylinder. When the swinging system 1, 2, 3, 4, 5 is shiftedto the left the supqly] supply of brake fluid to the outlet 14 throughspool Sis interrupted. When mass 3, part 4 and spool 5 are shifted tothe left the volume of chamber 10 will increase, brake fluid therebybeing pumped from the brake cylinder of the wheel due to the fact that apressure decrease takes place within outlet 14. A passage 17 connectschambers 9 and for the purpose of equalizing the pressure within thesetwo chambers. Functionally, the modification sbown shown in FIG. 4 isfully equivalent to the basic embodiment [shwon] shown in FIG. 1 inspite of the fact that ball 8 and spring 12 have been eliminated andreplaced by the valve spool formed by end portion 5 of part 4, thisvalve spool performing the same function as ball 8 and spring 12. Herebythe number of movable parts has been reduced and a still more compactembodiment of the device has been obtained.

The transfer device acting between the system 'comprising the springelement 2 and the heavy mass 3, on the one hand, and the control valveunit, on the other hand, comprises in the embodiment according to FIG. 5a rod 19 which at its end. remote from the mass 3 is provided with a cammember 20. A cam follower 21 is in contact with the cam curve of the cammember.

When the transfer device 19 is shifted from its equilibrium position thecam follower 21 will be lifted upwardly from the position shown in FIG.5. Due to this movement the cam follower will displace the rod 4connected to the slide valve body 5.

In the embodiment shown in FIG. 6 spring 2 is connected to a heavyswinging mass 3 journalled for oscillating movement about a center 22.In this embodiment the valve unit is a ball valve comprising a ball 8adapted to seal against a seat 7. Chambers 10 and 9 of the valve are inmutual communication via a passage 7a through which a reduced portion ofcontrol rod 4 extends. At the end of a rod 4 remote from the valve alink 27 is attached for swinging movement about pivot 28, the free endof the link being attached at pivotal point 26 to the swinging mass 3.At the critical natural resonant frequency of the system an increase ofamplitude will occur which causes the swinging mass to oscillate aboutthe center 22. Hereby rod 4 will be imparted a reciprocating movementwhich will control the closing of valve 11 by permitting ball 8 whichpreviously had been pushed off the seat by the reduced end of rod 4 tocome into sealing contact with seat 7 and thereby to close theapplication of braking pressure. Thereafter the volume of chamber 9 willbe increased by rod 4 being shifted to the left in FIG. 6, whereby thepressure applied to the wheel brake cylinder will be released in asimilar way as previously described.

In the embodiment according to FIG. 7 the transfer device has beenmodified in such a way that the swing ing mass 3 which also here isadapted to oscillate about a central pivot 22 is provided with a camsurface 20 against which a cam follower 21 abuts. The cam follower,which is shown in the form of a spherical body, e.g. a ball bearing orthe like, is connected with rod 4 which in turn in a way previouslydescribed extends into an actuates valve unit II. A spring 23 isinserted between the valve and an abutment such as to urge the camfollower against the cam surface and to maintain constant contactbetween the cam follower and the cam surface.

FIGS. 8A and 8B show a modified arrangement in which, on the one hand,the previously shown and described coil spring 2 has been replaced by atorsion spring and, on the other hand, rod 4 is positively guided in agroove in the swinging mass 3, said groove forming the equivalent of camsurface 20 of the previous embodiments. This modified embodiment willoperate exactly as the previously described embodiment.

In FIG. 9 there is shown an embodiment in which only the transfer deviceis modified in relation to previously described embodiments. At its endremote from the valve rod 4 is provided with an abutment plate 24abutting against a spherical body 25 attached to the swinging mass.During oscillating movement of the swinging mass 3 the spherical body 25will move along an arc ofa circle having the radius of the swinging mass3 causing the abutment plate 24 to move over the distance indicated inthe FIG. as the swinging mass is oscillating between the positionsindicated in broken lines. A spring 23 is adapted to press abutmentplate 24 into constant contact with the spherical body 25.

FIGS. A, B and C are different views of one embodiment of the inventionwhich comprises the same basic elements as the embodiment according toFIG. 8, however, with cam surface arranged on the side surface of theswinging mass 3 rather than on its peripheral edge as in FIG. 8. Herebya more compact construction is obtained due to the fact that the valveunit will be disposed at right angles to the plane of [oscilation 10scu'latirm of the swinging mass.

In FIG. 11 there is shown an embodiment in which the transfer devicetakes the form of a stiff resilient blade 41 which is attached to theperiphery of the swinging mass 3. The resilient blade 41 passes througha guide means 42 to a link system 43 connecting the resilient blade 41with rod 4 controlling the operation of valve 11. In the embodimentshown in FIG. 11 the ad vantage is obtained that if for some reasonblade 4I will crack, the braking fluid supply to the valve will closeball valve 8 so that no braking action can be applied to the wheelserved by the system shown. In order to avoid any risk due to the factthat the driver of the vehicle who relies upon the action of the brakecontrol system according to the present invention will be panic strickenby unexpected locking of the rear wheels during braking, the embodimentaccording to FIG. 11

causes the braking action to cease also in connection with mechanicalfaults and the locking risk unexpected and therefor still more dangerousis thus ruled out also in cases where such a fault occurs.

In spite of the fact that the practical tests made so far have shownthat a great amount ofslip," ie. the ratio between the speed of thevehicle and the rotational velocity of the wheel in a certain moment,does not appear to impair the directional stability of the vehicle,continued research and development may show that decreased slip"improves directional stability. For this purpose. according to thepresent invention, there is provided a device causing the impulsegenerator frequency to be changed down thereby more quickly to bringabout the desirable release of the braking action on the wheel. Herebythe wheel velocity will be successively reduced and "slip" of the wheelwill become sub stantially constant rather than having a very greatvalue in an initial phase with this value successively decreasing independance on the decrease of vehicle speed, the

device according to the present invention without a change down deviceof the type here in question normally yielding a substantially constantpredetermined rotational velocity of the wheel.

A device suited for this specific purpose of reducing the frequency ofthe impulse generator is shown in FIGS. [2A and B, this devicecomprising an input shaft which is imparted a turning movementproportional to the angular velocity of the wheel. A second shaft 32 isrigidly attached at right angles to shaft 30, planet wheels being freelyrotatable on the free ends of this second shaft 32. These planet wheelsare adapted to couple, on the one hand, a flywheel unit comprising afall cogwheel 33 journalled on shaft 30 by means of a bearing 31 andhaving a heavy mass 34 and, on the other hand, a second cogwheel 36adapted to rotate in relation to shaft 30 by means of a clutch 38.

Cogwheel 33 is provided with a cam surface 37 against which the sensingdevice I is adapted to abut. Said clutch 38, which for example may be afriction clutch, must be adapted to transmit the power required toenable cogwheel 36 and its cam surface 37 to drive cam follower 1.However, clutch 38 must also permit a relative movement between cogwheel36 with its cam element 37 and shaft 30 in order that the functiondescribed hereafter shall be obtained. During normal operation and lightbraking the unit shown is driven at the same speed as the input shaft30. However, upon a powerful retardation the flywheel unit 33, 34 willcontinue to rotate with a speed in excess of that of shafts 30 and 32due to the fact that the unit is rotatably supported by shaft 30. Shaft32 attached to shaft 30, however, will continue to rotate at the samerotational speed as shaft 30 so that planet wheels 35 will transfer areverse relative movement to cogwheel 36, which thus will rotate at alower speed as compared with input shaft 30. Hereby cam surface 37 willmore quickly reach the speed corresponding to the critical naturalresonant frequency of the system in accordance with the curve shown inFIG. 13. In the diagram of FIG. 13 the number of revolutions is shown asa function of time, the upper curve showing the speed of the vehicle,whereas the speed of the impulse generator is shown by the lower curvewhich is shown to extend in a zigzag fashion down to the critical numberof revolutions where the brake effect is released in accordance with theprevious description, up again to the same velocity as the wheel andthereafter the generator speed will again decrease down to the criticalfrequency of the system and so on. Thus, the wheel will be imparted aspeed decreasing in a stepwise fashion as indicated by the heavy centralcurve showing that the wheel will be imparted a lower speed than thevehicle but not a speed below the angular velocity value correspondingto the critical natural resonant frequency of the system.

In FIG. 14 there is shown an embodiment of the invention which isextremely compact and adapted to be disposed immediately adjacent therear wheel of a vehicle. As to its function the construction shown inthis Figure is in agreement with the previously described embodiment,however, the design is particularly corn pact and protected to withstandthe stresses inherent in the specific position of use.

The embodiments described in connection with FIGS. 5-14 have theadditional advantages that a well defined equilibrium position isobtained for the swing' ing system, that the braking pressure appliedcannot act on the swinging system but will be absorbed in bearings orthe like I and that many constructive problems are solved such asproblems in connection with the journalling of the movable parts used.

The invention has been shown and described in con nection with brakesystems for a motor vehicle. How ever, the invention may be used also inconnection with any hydraulic or pneumatic servo-system and on any fieldwhere a rotating wheel is to be braked and where locking of the wheelduring braking is undesirable. Examples of such fields of use arefeeding devices for material in the form of tapes, webs or wire where inmany cases a braking effect is desirable while at the same time alocking of the rotating wheels will be detrimental. Thus, theembodiments shown and described do not involve a limitation of thepresent invention the scope of which is exclusively defined in theattached claims.

What we claim is:

1. In a rotatable wheel and fluid-pressure actuated brake means forbraking rotation of the wheel, the combination therewith of mechanicalcontrol means for preventing the wheel from locking during braking andcomprising.

motion-transmitting means operatively coupled to said wheel andresponsive to rotation thereof for moving in pulsation at frequenciesproportional to the rotational speed of said wheel and including afrequency sensitive driven vibrating means having a predeterminedresonant frequency and being responsive to rotation of said wheel at apredetermined speed for displacement of one component of said vibratingmeans through a predetermined amplitude during forced vibration of saidvibrating means at said predetermined resonant frequency, and

braking effect varying means operatively connected to said vibratingmeans and to said brake means and including fluid flow control meansresponsive to displacement of said one component through saidpredetermined amplitude for precluding increase in braking effectexerted on said wheel while said wheel is rotating at the speed whichcauses forced vibration of said vibrating means at said predeterminedresonant frequency and thereby avoiding locking of the wheel duringbraking.

2. The combination according to claim 1 wherein said motion transmittingmeans comprises a cam member and a cam follower cooperating for movingsaid cam follower with pulsations proportional to the rotational speedof the wheel.

3. The combination according to claim 2 wherein said cam member and camfollower cooperate for moving said cam follower with sinusoidalmovement.

4. The combination according to claim 1 wherein said vibrating means andsaid fluid flow control means cooperate during pulsating movement ofsaid motion transmittingmeans at frequencies above and below saidresonant frequency by unvaryingly passing the pressure of fluidactuating said brake means.

5. The combination according to claim 1 wherein said vibrating meanscomprises an oscillating system of a mass and a spring coupled to saidmass for transmitting pulsating movement thereto, said mass and saidspring responding to driving pulsations of varying frequencies byvarying the amplitude of displacement of said mass.

6. The combination according to claim 5 wherein said mass of saidvibrating means is operatively connected to said fluid flow controlmeans of said brake effect varying means for periodically interruptingpressure fluid supply to said brake means and for releasing said wheelfrom applied brake action in response to movement of said mass through apredetermined amplitude of displacement.

7. The combination according to claim 6 wherein said mass and said fluidflow control means when actuated cooperate for releasing applied brakeaction during a period of time longer than the period of time duringwhich applied brake action is maintained.

8. The combination according to claim 5 further comprising meansmounting said oscillating system of a mass and a spring for linearoscillating movement of said mass.

9. The combination according to claim 5 further comprising meansmounting said oscillating system of a mass and a spring for rotaryoscillating movement of said mass.

10. The combination according to claim 5 wherein said mass and springare related one to another and to the angular velocity of the wheel inaccordance with the formula on V k/m where 0) denotes the angularvelocity of the wheel at the resonant frequency, k denotes the springconstant and m denotes the mass.

11. The combination according to claim 1 wherein said fluid flow controlmeans comprises a housing defining inlet chamber means for flow of brakeactuating fluid thereinto and outlet chamber means for flow ofbrake-actuating fluid therefrom, valve means for controlling flow offluid from said inlet chamber means to said outlet chamber means, andmeans for varying the volume of said outlet chamber means for therebyreducing the pressure of fluid actuating said brake means and furtherwherein said volume-varying means and said valve means cooperate inresponding to movement of said vibrating means for alternatelyincreasing and decreasing the braking effect applied to said wheel.

12. The combination according to claim ll wherein said valve meanscomprises a valve spool.

l3. The combination according to claim ll wherein said valve meanscomprises a ball valve.

14. The combination according to claim 13 wherein said ball valvecomprises a valve seat interposed be tween said inlet and said outletchamber means, a ball member and means biasing said ball member toward aseated position on said valve seat.

15. The combination according to claim 1 wherein saidmotion-transmitting means comprises means for increasing the frequencyof pulsating movement relative to the rotational speed of the wheel.

16. The combination according to claim 15 wherein saidfrequency-increasing means comprises a cam surface and a cooperating camfollower.

17. The combination according to claim 15 wherein saidfrequency-increasing means comprises a link systern.

IS. The combination according to claim I wherein said motiontransmitting means comprises means for decreasing the frequency ofpulsating movement rela tive to the rotational speed of the wheel.

19. The combination according to claim 18 wherein saidfrequency-decreasing means comprises planetary transmission meansoperatively interposed between said wheel and said vibrating means, saidplanetary transmission means including a driven shaft coupled to saidwheel for rotation therewith, output gear means coupled to saidvibrating means for transmittal of pulsating movement thereto,overrunning clutch means for coupling said driven shaft and said outputgear means together upon the rotational speed of said driven shaftexceeding that of said output gear means, planet gear means carried bysaid driven shaft for rotation therewith and meshing with said outputgear means, and inertial gear means meshing with said planet gear meansand coupled thereby to said output gear means, and inertial gear meansbeing driven from said driven shaft through said planetary gear meansupon said clutch means effecting coupling of said output gear means andsaid driven shaft and said inertial gear means driving said output gearmeans through said planetary gear means upon said clutch means effectinguncoupling of said output gear means and said driven shaft.

20. In a rotatable wheel and fluid-pressure actuated brake meansforbraking rotation of the wheel, the combination therewith of controlmeans for preventing the wheel from locking during braking andcomprising:

a mass supportedfor linear oscillating movement in alternate directionsfrom an equilibrium position,

spring means operatively connected with said massfor defining therewitha swinging system andfor imposin g on said mass force biasing said masstoward said equilibrium position,

said swinging system responding to vibration at a resonant frequency bydisplacing said mass through more than a predetermined amplitude inalternate directionsfrom the equilibrium position and responding tovibration at any frequency other than said resonant frequency by failingto displace said mass through said predetermined amplitude, and

valve means operable between flow permitting and flow blocking positionsand operatively connected with said mass for being maintained in flowpermitting position while said mass is in said equilibrium position andwith said brake meansfor responding to displacement of said mass throughat least said predetermined amplitude by moving front flow permittingposition to flow blocking position and thereby interrupting brakingeflect exerted on said wheel.

21. In a rotatable wheel and fluid-pressure actuated brake meansforbraking rotation ofthe wheel, the combi nation therewith of controlmeans for preventing the wheel from locking during braking andcomprising:

a mass supported for rotary oscillating movement in alternate directionsfrom an equilibrium position.

spring means operatively connected with said mass for defining therewitha swinging system andfor imposing on said mass force biasing said masstoward said equilibrium position,

said swinging system responding to vibration at a resonan! frequency bydisplacing said mass through more than a predetermined amplitude inalternate directions from the equilibrium position and responding tovibration at any frequency other than said resonant frequency by failingto displace said mass through said predetermined amplitude, and

valve means operable between flow permitting and flow blocking positionsand operatively connected with said massfor being maintained in flowpermitting position while said mass is in said equilibrium position andwith said brake means for responding to displacement of said massthrough at least said predetermined amplitude by moving from flowpermitting position to flow blocking position and thereby interruptingbraking effect exerted on said wheel.

22. In a rotatable wheel and fluid-pressure actuated brake means forbraking rotation of the wheel, the combination therewith of controlmeans for preventing the wheel from locking during braking andcomprising:

a mass supported for rotary oscillating movement about a predeterminedaxis and in alternate direc tions front an equilibrium position,

helical torsion spring means mounted concentrically with saidpredetermined axis and operatively com nected with said mass fordefining therewith a swinging system and for imposing on said mass forcebiasing said mass toward said equilibrium position, said swinging systemresponding to vibration at a resonant frequency by displacing said massthrough more than a predetermined amplitude in alternate directions fromthe equilibrium position and responding to vibration at any frequencyother than said resonant frequency by failing to displace said massthrough said predetermined amplitude, and

valve means operable between flow permitting and flow blocking positionsand operatively connected with said mass for being maintained in flowpermitting position while said mass is in said equilibrium position andwith said brake means for responding to displacement of said massthrough at least said predetermined amplitude by moving from flowpermitting position to flow blocking position and thereby interruptingbraking effect exerted on said wheel.

23. In a rotatable wheel and fluid-pressure actuated brake means forbraking rotation of the wheel, the combination therewith of controlmeans for preventing the wheel from locking during braking andcomprising:

a mass supported for rotary oscillating movement about a predeterminedaxis and in alternate directions from an equilibrium position,

helical torsion spring means mounted concentrically with saidpredetermined axis and operatively connected with said mass for definingtherewith a swinging system and for imposing on said mass force biasingsaid mass toward said equilibrium position,

said swinging system responding to vibration at a resonantfrequency bydisplacing said mass through more than a predetermined amplitude inalternate directions from the equilibrium position,

cam surface means mounted on said mass for movement therewith about saidpredetermined axis,

cam follower means for engaging said cam surface means and mounted forlinear reciprocation in coordination with rotary oscillating movement ofsaid cam surface means and said mass, and

valve means operable between flow permitting and flow blocking positionsand operatively connected with said cam follower means for beingmaintained in flow permitting position while said mass is in saidequilibrium position and with said brake means for responding todisplacement of said mass through at least said predetermined amplitudeby moving from flow permitting position to flow blocking position andthereby interrupting braking effect exerted on said wheel.

24. In a rotatable wheel and fluid-pressure actuated brake meansforbraking rotation of the wheel, the combination therewith of controlmeans for preventing the wheel from locking during braking andcomprising:

a mass supported for oscillating movement in alternate directions froman equilibrium position,

spring means operatively connected with said mass for forming therewitha swinging system, said spring means imposing on said mass a forcebiasing said mass toward said equilibrium position,

said swinging system when vibrating at its resonant frequency displacingsaid mass through more than a flow blocking amplitude in alternatedirections from the equilibrium position, valve housing means forpassing pressurized brake actuating fluid to said brake means, and

means mounted in said housing means for movement between a firstposition in which brake fluid flow through said housing means ispermitted and asecond position in which broke fluidflow through saidhousing means is blocked and pressure applied to said brake means isreleased, said movable means being operatively connected l to said massfor normally being maintained in saidfirst position andfor being movedto said second position when said mass is displaced through more thansaid flow blocking amplitude in at least one of said alternatedirections,

said flow blocking amplitude being the minimum amplitude at which brakefluidflow through said housing means is blocked. 25. In a rotatablewheel and fluid-pressure actuated brake meansfor braking rotation of thewheel, the combination therewith of control means for preventing thewheel from locking during braking and comprising.

a mass supported for rotary oscillating movement in alternate directionsfrom an equilibrium position, helical tor sion spring means operativelyconnected with said massforforming therewith a swinging system, saidspring means imposing on said mass a force biasing said mass toward saidequilibrium 'position,

said swinging system when vibratingat its resonant frequency displacingsaid mass through more than a flow blocking amplitude in alternatedirections from the equilibrium position, valve housing means forpassing pressurized brake actuating fluid to said brake means, and

means mounted in said housing means for movement between a firstposition in which brake fluid flow through said housing means ispermitted and a second position in which brake fluid flow through saidhousing means is blocked and pressure applied to said brake means isreleased, said movable means being operatively connected to said massfor normally being maintained in saidfirst position andfor being movedto said second position when said mass is displaced through more thansaid flow blocking amplitude in both of said alternate directions,

said flow blocking amplitude being the minimum amplitude at whichbrakefluidflow through said housing means is blocked.

26. In a rotatable wheel and fluidpressure actuated brake meansforbraking rotation of the wheel, the combination therewith of controlmeans for preventing the wheelfrom locking during braking andcomprising:

a mass supported for oscillating movement in alternate directions froman equilibrium position,

spring means operatively connected with said mass for forming therewitha swinging system, said spring means imposing on said mass force biasingsaid mass toward said equilibrium position,

motive means operatively connected with said swinging system for causingsaid swinging system to vibrate at its resonant frequency,

said swinging system when vibrating at its resonant frequency displacingsaid mass through more than a flow blocking amplitude in alternatedirections from the equilibrium position,

valve housing means for passing pressurized brake actuating fluid tosaid brake means, and

means mounted in said housing means for movement between a firstposition in which brake fluid flow through said housing means ispermitted and a second position in which brake fluidflow through said vl tousingmeans is blocked and pressure applied to said ,brake means isreleased. said movable means being operatively connected to said massfor normally being maintained in said first position and for being movedto said second position when said mass is displaced through more -thansaid flow blocking amplitudein at least one of said alternatedirections,

saidflow blocking amplitude being the minimum amplitude at which brakefluid flow through said housing means, is blocked.

27. In a-rotatable wheel and fluid-pressure actuated brake means forbraking rotation of the wheel, the combination therewith of controlmeans for preventing the wheelfrom locking during braking andcomprising:

a mass supportedfor oscillating movement in alternate directions from anequilibrium position,

spring means operatively connected with said mass for forming therewitha swinging system, said spring means imposing on said mass a forcebiasing said masstoward said equilibrium position, motive meansoperatively connected with said swing ing system and said wheel andresponsive to predetermined movement of said wheel for causing saidswinging system to vibrate at its resonantfrequency,

said swinging system when vibrating at its resonant frequency displacingsaid mass through more than a flow blocking amplitude in alternatedirections from the equilibrium position,

valve housing means for passing pressurized brake actuating fluid tosaid brake means, and means mounted in said housing means for movementbetween a first position in which brake fluid flow through said housingmeans is permitted and a second position in which broke fluidflowthrough said housing means is blocked and pressure applied to said brakemeans is released, said movable means being operatively connected tosaid mass for normally being maintained in saidfirst position and forbeing moved to said second position when said mass is displaced throughmore than said flow blocking amplitude in at least one of said alternatedirections,

said flow blocking amplitude being the minimum amplitude at which brakefluidflow through said housing means is blocked.

28. Apparatusfor controllably interrupting and releasingfluid pressureapplied through a valve housing means and comprising:

a mass supported for oscillating movement in alternate directions froman equilibrium position,

spring means operatively connected to said mass for forming therewith aswinging system, said spring means imposing on said mass a force biasingsaid mass toward said equilibrium position.

said swinging system when vibrating at its resonant frequency displacingsaid mass through more than a flow blocking amplitude in alternatedirections front the equilibrium position,

valve housing means for passing actuating fluid, and

means mounted in said housing means for movement between a firstposition in which actuatingfluid flow through said housing means ispermitted and a sec and position in which actuating fluid flow throughsaid housing is blocked and pressure applied through said housing meansis released, said movable means being operatively connected to said massfor normally being maintained in saidfirst position andfor being movedto said second position when said mass is displaced through more thansaid flow blocking amplitude in at least one of said alternatedirections,

said flow blocking amplitude being the minimum amplitude at which fluidflow through said housing means is blocked. 29. Apparatus forcontrollably interrupting and releasing fluid pressure applied through avalve housing means and comprising:

a mass supported for rotary oscillating movement in alternate directionsfrom an equilibrium position, helical torsion spring means operativelyconnected to said mass for forming therewith a swinging system, saidspring means imposing on said mass a force biasing said mass toward saidequilibrium position,

said swinging system when vibrating at its resonant frequency displacingsaid mass through more than a flow blocking amplitude in alternatedirections from the equilibrium position,

valve housing means for passing actuating fluid, and

means mounted in said housing means for movement between a firstposition in which actuating fluid flow through said housing means ispermitted and a second position in which actuating fluid flow throughsaid housing is blocked and pressure applied through said housing meansis released, said movable means being operatively connected to said massfor normally being maintained in saidfirst position andfor being movedto said second position when said mass is displaced through more thansaid flow blocking amplitude in both of said alternate directions,

said flow blocking amplitude being the minimum amplitude at which fluidflow through said housing means is blocked.

30. Apparatus for controllably interrupting and releasing fluid pressureapplied through a valve housing means and comprising:

a mass supported for oscillating movement in alternate directions froman equilibrium position,

spring means operatively connected to said mass for forming therewith aswinging system, said spring means imposing on said mass a force biasingsaid mass toward said equilibrium position,

motive means operatively connected with said swinging system for causingsaid system to vibrate at its resonant frequency,

said swinging system when vibrating at its resonant frequency displacingsaid mass through more than a flow blocking amplitude in alternatedirections from the equilibrium position,

valve housing means for passing actuating fluid, and

means mounted in said housing means for movement between a firstposition in which actuating fluid flow through said housing means ispermitted and a second position in which actuating fluid flow throughsaid housing is blocked and pressure applied through said housing meansis released, said movable means being operatively connected to said massfor normally being maintained in said first position and for being movedto said second position when said mass is displaced through more thansaid flow blocking amplitude in at least one of said alternatedirections, said flow blocking amplitude being the minimum amplitude atwhich fluid flow through said housing means is blocked.

1. In a rotatable wheel and fluid-pressure actuated brake means forbraking rotation of the wheel, the combination therewith of mechanicalcontrol means for preventing the wheel from locking during braking andcomprising: motion-transmitting means operatively coupled to said wheeland responsive to rotation thereof for moving in pulsation atfrequencies proportional to the rotational speed of said wheel andincluding a frequency sensitive driven vibrating means having apredetermined resonant frequency and being responsive to rotation ofsaid wheel at a predetermined speed for displacement of one component ofsaid vibrating means through a predetermined amplitude during forcedvibration of said vibrating means at said predetermined resonantfrequency, and braking effect varying means operatively connected tosaid vibrating means and to said brake means and including fluid flowcontrol means responsive to displacement of said one component throughsaid predetermined amplitude for precluding increase in braking effectexerted on said wheel while said wheel is rotating at the speed whichcauses forced vibration of said vibrating means at said predeterminedresonant frequency and thereby avoiding locking of the wheel duringbraking.
 2. The combination according to claim 1 wherein said motiontransmitting means comprises a cam member and a cam follower cooperatingfor moving said cam follower with pulsations proportional to therotational speed of the wheel.
 3. The cOmbination according to claim 2wherein said cam member and cam follower cooperate for moving said camfollower with sinusoidal movement.
 4. The combination according to claim1 wherein said vibrating means and said fluid flow control meanscooperate during pulsating movement of said motion transmitting-means atfrequencies above and below said resonant frequency by unvaryinglypassing the pressure of fluid actuating said brake means.
 5. Thecombination according to claim 1 wherein said vibrating means comprisesan oscillating system of a mass and a spring coupled to said mass fortransmitting pulsating movement thereto, said mass and said springresponding to driving pulsations of varying frequencies by varying theamplitude of displacement of said mass.
 6. The combination according toclaim 5 wherein said mass of said vibrating means is operativelyconnected to said fluid flow control means of said brake effect varyingmeans for periodically interrupting pressure fluid supply to said brakemeans and for releasing said wheel from applied brake action in responseto movement of said mass through a predetermined amplitude ofdisplacement.
 7. The combination according to claim 6 wherein said massand said fluid flow control means when actuated cooperate for releasingapplied brake action during a period of time longer than the period oftime during which applied brake action is maintained.
 8. The combinationaccording to claim 5 further comprising means mounting said oscillatingsystem of a mass and a spring for linear oscillating movement of saidmass.
 9. The combination according to claim 5 further comprising meansmounting said oscillating system of a mass and a spring for rotaryoscillating movement of said mass.
 10. The combination according toclaim 5 wherein said mass and spring are related one to another and tothe angular velocity of the wheel in accordance with the formula omegaSquare Root k/m where omega denotes the angular velocity of the wheel atthe resonant frequency, k denotes the spring constant and m denotes themass.
 11. The combination according to claim 1 wherein said fluid flowcontrol means comprises a housing defining inlet chamber means for flowof brake actuating fluid thereinto and outlet chamber means for flow ofbrake-actuating fluid therefrom, valve means for controlling flow offluid from said inlet chamber means to said outlet chamber means, andmeans for varying the volume of said outlet chamber means for therebyreducing the pressure of fluid actuating said brake means and furtherwherein said volume-varying means and said valve means cooperate inresponding to movement of said vibrating means for alternatelyincreasing and decreasing the braking effect applied to said wheel. 12.The combination according to claim 11 wherein said valve means comprisesa valve spool.
 13. The combination according to claim 11 wherein saidvalve means comprises a ball valve.
 14. The combination according toclaim 13 wherein said ball valve comprises a valve seat interposedbetween said inlet and said outlet chamber means, a ball member andmeans biasing said ball member toward a seated position on said valveseat.
 15. The combination according to claim 1 wherein saidmotion-transmitting means comprises means for increasing the frequencyof pulsating movement relative to the rotational speed of the wheel. 16.The combination according to claim 15 wherein said frequency-increasingmeans comprises a cam surface and a cooperating cam follower.
 17. Thecombination according to claim 15 wherein said frequency-increasingmeans comprises a link system.
 18. The combination according to claim 1wherein said motion transmitting means comprises means for decreasingthe frequency of pulsating movement relative to the rotational speed ofthe wheel.
 19. The combination according to claim 18 wherein saidfrequency-decreasing means comprises planetary transmission meansoperatively interposed between said wheel and said vibrating means, saidpLanetary transmission means including a driven shaft coupled to saidwheel for rotation therewith, output gear means coupled to saidvibrating means for transmittal of pulsating movement thereto,overrunning clutch means for coupling said driven shaft and said outputgear means together upon the rotational speed of said driven shaftexceeding that of said output gear means, planet gear means carried bysaid driven shaft for rotation therewith and meshing with said outputgear means, and inertial gear means meshing with said planet gear meansand coupled thereby to said output gear means, and inertial gear meansbeing driven from said driven shaft through said planetary gear meansupon said clutch means effecting coupling of said output gear means andsaid driven shaft and said inertial gear means driving said output gearmeans through said planetary gear means upon said clutch means effectinguncoupling of said output gear means and said driven shaft.
 20. In arotatable wheel and fluid-pressure actuated brake means for brakingrotation of the wheel, the combination therewith of control means forpreventing the wheel from locking during braking and comprising: a masssupported for linear oscillating movement in alternate directions froman equilibrium position, spring means operatively connected with saidmass for defining therewith a swinging system and for imposing on saidmass force biasing said mass toward said equilibrium position, saidswinging system responding to vibration at a resonant frequency bydisplacing said mass through more than a predetermined amplitude inalternate directions from the equilibrium position and responding tovibration at any frequency other than said resonant frequency by failingto displace said mass through said predetermined amplitude, and valvemeans operable between flow permitting and flow blocking positions andoperatively connected with said mass for being maintained in flowpermitting position while said mass is in said equilibrium position andwith said brake means for responding to displacement of said massthrough at least said predetermined amplitude by moving from flowpermitting position to flow blocking position and thereby interruptingbraking effect exerted on said wheel.
 21. In a rotatable wheel andfluid-pressure actuated brake means for braking rotation of the wheel,the combination therewith of control means for preventing the wheel fromlocking during braking and comprising: a mass supported for rotaryoscillating movement in alternate directions from an equilibriumposition, spring means operatively connected with said mass for definingtherewith a swinging system and for imposing on said mass force biasingsaid mass toward said equilibrium position, said swinging systemresponding to vibration at a resonant frequency by displacing said massthrough more than a predetermined amplitude in alternate directions fromthe equilibrium position and responding to vibration at any frequencyother than said resonant frequency by failing to displace said massthrough said predetermined amplitude, and valve means operable betweenflow permitting and flow blocking positions and operatively connectedwith said mass for being maintained in flow permitting position whilesaid mass is in said equilibrium position and with said brake means forresponding to displacement of said mass through at least saidpredetermined amplitude by moving from flow permitting position to flowblocking position and thereby interrupting braking effect exerted onsaid wheel.
 22. In a rotatable wheel and fluid-pressure actuated brakemeans for braking rotation of the wheel, the combination therewith ofcontrol means for preventing the wheel from locking during braking andcomprising: a mass supported for rotary oscillating movement about apredetermined axis and in alternate directions from an equilibriumposition, helical tOrsion spring means mounted concentrically with saidpredetermined axis and operatively connected with said mass for definingtherewith a swinging system and for imposing on said mass force biasingsaid mass toward said equilibrium position, said swinging systemresponding to vibration at a resonant frequency by displacing said massthrough more than a predetermined amplitude in alternate directions fromthe equilibrium position and responding to vibration at any frequencyother than said resonant frequency by failing to displace said massthrough said predetermined amplitude, and valve means operable betweenflow permitting and flow blocking positions and operatively connectedwith said mass for being maintained in flow permitting position whilesaid mass is in said equilibrium position and with said brake means forresponding to displacement of said mass through at least saidpredetermined amplitude by moving from flow permitting position to flowblocking position and thereby interrupting braking effect exerted onsaid wheel.
 23. In a rotatable wheel and fluid-pressure actuated brakemeans for braking rotation of the wheel, the combination therewith ofcontrol means for preventing the wheel from locking during braking andcomprising: a mass supported for rotary oscillating movement about apredetermined axis and in alternate directions from an equilibriumposition, helical torsion spring means mounted concentrically with saidpredetermined axis and operatively connected with said mass for definingtherewith a swinging system and for imposing on said mass force biasingsaid mass toward said equilibrium position, said swinging systemresponding to vibration at a resonant frequency by displacing said massthrough more than a predetermined amplitude in alternate directions fromthe equilibrium position, cam surface means mounted on said mass formovement therewith about said predetermined axis, cam follower means forengaging said cam surface means and mounted for linear reciprocation incoordination with rotary oscillating movement of said cam surface meansand said mass, and valve means operable between flow permitting and flowblocking positions and operatively connected with said cam followermeans for being maintained in flow permitting position while said massis in said equilibrium position and with said brake means for respondingto displacement of said mass through at least said predeterminedamplitude by moving from flow permitting position to flow blockingposition and thereby interrupting braking effect exerted on said wheel.24. In a rotatable wheel and fluid-pressure actuated brake means forbraking rotation of the wheel, the combination therewith of controlmeans for preventing the wheel from locking during braking andcomprising: a mass supported for oscillating movement in alternatedirections from an equilibrium position, spring means operativelyconnected with said mass for forming therewith a swinging system, saidspring means imposing on said mass a force biasing said mass toward saidequilibrium position, said swinging system when vibrating at itsresonant frequency displacing said mass through more than a flowblocking amplitude in alternate directions from the equilibriumposition, valve housing means for passing pressurized brake actuatingfluid to said brake means, and means mounted in said housing means formovement between a first position in which brake fluid flow through saidhousing means is permitted and a second position in which brake fluidflow through said housing means is blocked and pressure applied to saidbrake means is released, said movable means being operatively connectedto said mass for normally being maintained in said first position andfor being moved to said second position when said mass is displacedthrough more than said flow blocking amplitude in at least one of saidalternate directionS, said flow blocking amplitude being the minimumamplitude at which brake fluid flow through said housing means isblocked.
 25. In a rotatable wheel and fluid-pressure actuated brakemeans for braking rotation of the wheel, the combination therewith ofcontrol means for preventing the wheel from locking during braking andcomprising: a mass supported for rotary oscillating movement inalternate directions from an equilibrium position, helical torsionspring means operatively connected with said mass for forming therewitha swinging system, said spring means imposing on said mass a forcebiasing said mass toward said equilibrium position, said swinging systemwhen vibrating at its resonant frequency displacing said mass throughmore than a flow blocking amplitude in alternate directions from theequilibrium position, valve housing means for passing pressurized brakeactuating fluid to said brake means, and means mounted in said housingmeans for movement between a first position in which brake fluid flowthrough said housing means is permitted and a second position in whichbrake fluid flow through said housing means is blocked and pressureapplied to said brake means is released, said movable means beingoperatively connected to said mass for normally being maintained in saidfirst position and for being moved to said second position when saidmass is displaced through more than said flow blocking amplitude in bothof said alternate directions, said flow blocking amplitude being theminimum amplitude at which brake fluid flow through said housing meansis blocked.
 26. In a rotatable wheel and fluid-pressure actuated brakemeans for braking rotation of the wheel, the combination therewith ofcontrol means for preventing the wheel from locking during braking andcomprising: a mass supported for oscillating movement in alternatedirections from an equilibrium position, spring means operativelyconnected with said mass for forming therewith a swinging system, saidspring means imposing on said mass a force biasing said mass toward saidequilibrium position, motive means operatively connected with saidswinging system for causing said swinging system to vibrate at itsresonant frequency, said swinging system when vibrating at its resonantfrequency displacing said mass through more than a flow blockingamplitude in alternate directions from the equilibrium position, valvehousing means for passing pressurized brake actuating fluid to saidbrake means, and means mounted in said housing means for movementbetween a first position in which brake fluid flow through said housingmeans is permitted and a second position in which brake fluid flowthrough said housing means is blocked and pressure applied to said brakemeans is released, said movable means being operatively connected tosaid mass for normally being maintained in said first position and forbeing moved to said second position when said mass is displaced throughmore than said flow blocking amplitude in at least one of said alternatedirections, said flow blocking amplitude being the minimum amplitude atwhich brake fluid flow through said housing means is blocked.
 27. In arotatable wheel and fluid-pressure actuated brake means for brakingrotation of the wheel, the combination therewith of control means forpreventing the wheel from locking during braking and comprising: a masssupported for oscillating movement in alternate directions from anequilibrium position, spring means operatively connected with said massfor forming therewith a swinging system, said spring means imposing onsaid mass a force biasing said mass toward said equilibrium position,motive means operatively connected with said swinging system and saidwheel and responsive to predetermined movement of said wheel for causingsaid swinging system to vibrate at its resonant freQuency, said swingingsystem when vibrating at its resonant frequency displacing said massthrough more than a flow blocking amplitude in alternate directions fromthe equilibrium position, valve housing means for passing pressurizedbrake actuating fluid to said brake means, and means mounted in saidhousing means for movement between a first position in which brake fluidflow through said housing means is permitted and a second position inwhich brake fluid flow through said housing means is blocked andpressure applied to said brake means is released, said movable meansbeing operatively connected to said mass for normally being maintainedin said first position and for being moved to said second position whensaid mass is displaced through more than said flow blocking amplitude inat least one of said alternate directions, said flow blocking amplitudebeing the minimum amplitude at which brake fluid flow through saidhousing means is blocked.
 28. Apparatus for controllably interruptingand releasing fluid pressure applied through a valve housing means andcomprising: a mass supported for oscillating movement in alternatedirections from an equilibrium position, spring means operativelyconnected to said mass for forming therewith a swinging system, saidspring means imposing on said mass a force biasing said mass toward saidequilibrium position, said swinging system when vibrating at itsresonant frequency displacing said mass through more than a flowblocking amplitude in alternate directions from the equilibriumposition, valve housing means for passing actuating fluid, and meansmounted in said housing means for movement between a first position inwhich actuating fluid flow through said housing means is permitted and asecond position in which actuating fluid flow through said housing isblocked and pressure applied through said housing means is released,said movable means being operatively connected to said mass for normallybeing maintained in said first position and for being moved to saidsecond position when said mass is displaced through more than said flowblocking amplitude in at least one of said alternate directions, saidflow blocking amplitude being the minimum amplitude at which fluid flowthrough said housing means is blocked.
 29. Apparatus for controllablyinterrupting and releasing fluid pressure applied through a valvehousing means and comprising: a mass supported for rotary oscillatingmovement in alternate directions from an equilibrium position, helicaltorsion spring means operatively connected to said mass for formingtherewith a swinging system, said spring means imposing on said mass aforce biasing said mass toward said equilibrium position, said swingingsystem when vibrating at its resonant frequency displacing said massthrough more than a flow blocking amplitude in alternate directions fromthe equilibrium position, valve housing means for passing actuatingfluid, and means mounted in said housing means for movement between afirst position in which actuating fluid flow through said housing meansis permitted and a second position in which actuating fluid flow throughsaid housing is blocked and pressure applied through said housing meansis released, said movable means being operatively connected to said massfor normally being maintained in said first position and for being movedto said second position when said mass is displaced through more thansaid flow blocking amplitude in both of said alternate directions, saidflow blocking amplitude being the minimum amplitude at which fluid flowthrough said housing means is blocked.
 30. Apparatus for controllablyinterrupting and releasing fluid pressure applied through a valvehousing means and comprising: a mass supported for oscillating movementin alternate directions from an equilibrium position, spring meansoperatively connected to said mass for forming therewith a swingingsystem, said spring means imposing on said mass a force biasing saidmass toward said equilibrium position, motive means operativelyconnected with said swinging system for causing said system to vibrateat its resonant frequency, said swinging system when vibrating at itsresonant frequency displacing said mass through more than a flowblocking amplitude in alternate directions from the equilibriumposition, valve housing means for passing actuating fluid, and meansmounted in said housing means for movement between a first position inwhich actuating fluid flow through said housing means is permitted and asecond position in which actuating fluid flow through said housing isblocked and pressure applied through said housing means is released,said movable means being operatively connected to said mass for normallybeing maintained in said first position and for being moved to saidsecond position when said mass is displaced through more than said flowblocking amplitude in at least one of said alternate directions, saidflow blocking amplitude being the minimum amplitude at which fluid flowthrough said housing means is blocked.